how many miles on your GTS Clos? Cause if its around 60K, you don't need to change the tranny fluid. It comes stock with 90 wieght, and that is pretty thick oil bro.
Redline MT90 - Shouldn't matter, oil is oil. Probably just a brand name or something. It might last longer, idk, never used it. Try it if you want, still won't hurt your car at the track or the street.